Wheelchair construction

ABSTRACT

A wheelchair capable of being constructed in several different sizes from components of standard size in order to permit users of different sizes and users with one or more handicaps to utilize such wheelchairs. The wheelchair includes a main frame and a foot support assembly which can be telescopically adjustably affixed to the main frame. In addition, a seat section can be telescopically adjustably affixed to the main frame such that the seat is located at a selected height and the foot support section can extend outwardly from the frame for a selected distance to accommodate users of differing height. The rear wheels are positionally mounted with respect to the main frame such that the rear wheels can be located in several different positions in order to change the overall center of gravity and the wheelbase of the wheelchair. In this way, the wheelchair can be used for conventional wheelchair movement, as well as for athletic activities. A pair of front wheels are also adjustably positionally mounted with respect to the main frame in order to change the angle of the wheelchair and the seat relative to the ground or other supporting surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to certain new and useful improvementsin wheelchairs, and more particularly, to improved wheelchairs which canbe constructed in a variety of sizes from standard size components andwhich also have front and back wheels adjustably mounted thereof.

2. Brief Description of the Prior Art

Wheelchair constructions have remained unchanged, except for relativelyminor features, for a substantial period of time. While wheelchairs haveexisted for many years, they generally were constructed of a main frame,front and rear wheels, side rails or so-called "arm rests" and footsupport members. However, there was no means for creating ormanufacturing a wheelchair of different sizes, at a relatively low cost,from standard sized components, in order to accommodate different sizeusers.

Prior art wheelchair manufacturers constructed several different sizedwheelchairs and used different sized components for each of thedifferently sized wheelchairs. In the case of a tall individual, themain frame had to be larger, the seat located in a different position,and a foot support member extended further from the seat, than in thecase of a wheelchair for a smaller individual. In addition, for thelarger sized wheelchair, the seat may have to have been located at ahigher elevation in order to permit the user to engage rims on thewheels for propelling the wheelchair in an easy and convenient manner.

Notwithstanding, heretofore there has not been any wheelchair which isdesigned for anything except normal transport. In other words,wheelchairs heretofore constructed were not designed to permit any formof athletic activity, and particularly, for fast-moving sportsactivities. This was primarily due to the fact that the prior artwheelchairs were all of a box-like construction with the seat, andhence, the center of gravity, located at a fixed and at a substantialdistance above the ground. Consequently, the prior art wheelchairs werenot designed for any fast movement, and if one attempted to propel anyof the prior art wheelchairs at any significant speed, or attempted toturn a corner quickly, the wheelchair might well tip over creatinginjury to the user.

In recent years, it has been found to be highly beneficial forparaplegics and others required to use wheelchairs on a relativelypermanent basis to engage in various forms of athletic activities,including wheelchair racing, tennis, and the like. However, thewheelchair constructions heretofore did not lend themselves to such formof activities.

For the more seriously handicapped people, particularly with high levelback injuries which limited the mobility of these handicapped persons'arms, the conventional wheelchairs are difficult to use. This is due tothe heavy construction and weight of the conventional wheelchairs whichmake it more difficult for the injured party to push and to manuever. Asa result, people with such injuries had to resort to the use of motorpowered wheelchairs, as for example, electric motor powered wheelchairswhich use a battery source of power. These motor powered wheelchairs arequite expensive and require periodic maintenance which thereby militatesagainst widespread use. Further, these wheelchairs require frequentrecharging when battery powered.

U.S. Pat. No. 3,937,490 to Nasr discloses a wheelchair having somedegree of adjustability to suit several body sizes and deformities.Particularly, the width of the seat and back rest panels may beadjusted, and the length of the seat may be adjusted. However, thispatent does not disclose a wheelchair which can be made from a commonmain frame and in a variety of commonly sized components which arecapable of being mounted in a desired location in the same manner astaught and claimed in the instant application. U.S. Pat. No. 4,046,374to Breyley discloses a walking aid which includes caster wheels. Inaddition, the walking aid is provided with telescopically locatedadjustable members.

OBJECTS OF THE INVENTION

It is, therefore, a primary object of the present invention to provide awheelchair which may be constructed of a main frame and a plurality ofcommonly sized auxiliary components adjustably attached to the mainframe in order to suit different sized users.

It is another object of the present invention to provide a wheelchair ofthe type stated in which a seat section can be adjustably attached tothe main frame in a variety of positions and a foot support member canbe adjustably attached to the main frame in a number of positions, andwith at least front or rear wheels capable of being adjustably attachedto the main frame in a variety of positions.

It is a further object of the present invention to provide a wheelchairof the type stated having rear wheels which are capable of being shiftedlongitudinally and vertically in order to change the wheel base of thewheelchair and vertically in order to change the angle of attack of thewheelchair.

It is an additional object of the present invention to provide awheelchair of the type stated in which the front wheels can beadjustably positioned, and in which a front wheel mounting means iscapable of receiving different sized front wheels.

It is still another object of the present invention to provide awheelchair construction of the type stated which is uniquely adapted fornormal use and also for athletic activities, by mere adjustment of thepositions of the wheels.

It is still another object of the present invention to provide a methodof manufacturing a wheelchair from a limited number of common componentssuch that the wheelchairs can be of differing sizes in order to suitdifferent sized users.

It is still a further object of the present invention to provide amethod of changing the wheel base and also changing the center ofgravity of a wheelchair in order to permit the same to be used in normaltransport activities and also for athletic activities.

With the above and other objects in view, my invention resides in thenovel features of form, construction, arrangement and combination ofparts presently described and pointed out in the claims.

SUMMARY OF THE DISCLOSURE

A wheelchair comprising a main frame, a seat structure, and a footsupport structure with the latter two components capable of beingadjustably positioned on the main frame. In this way, a wheelchairconstructed from commonly sized components can be made in a number ofdifferent sizes in order to suit differing sized users and users withdifferent forms of disabilities or deformities.

The main frame generally comprises a plurality of longitudinallyextending rigid members which are connected by a plurality oftransversely extending rigid members. A plurality of first uprightmembers are located on a rear portion of said frame, and a plurality ofsecond upright members are located on the front portion of said mainframe. The seat structure is capable of being attached to and adjustablypositioned on the main frame, as aforesaid. The seat structure iscomprised of a seat frame having a plurality of first posts capable ofbeing fitted with respect to a separate one of the first upright membersand adjustably located thereon. A seat pad is also carried by thisframe.

One of the other main components forming part of the wheelchair is thefoot support structure which is also capable of being attached to andadjustably positioned at a front portion of the main frame. The footsupport structure is comprised of a plurality of second posts with eachcapable of being fitted with respect to a separate one of the secondupright members. A foot receiving member is also carried by these secondposts. In this way, several different sized wheelchairs can beconstructed with commonly sized main frames and foot support structuresand seat structures.

The seat frame preferably has additional posts capable of being fittedwith respect to upper ends of the first upright tubular members as well.In another embodiment of the invention, the upright members and theposts are capable of being fitted with respect to one another andadjustably telescopically arranged. More specifically, the uprightmembers are tubular, and the posts are capable of being fitted withinthe open ends of the upright members.

In another embodiment of the invention, arm rests or side frames arecapable of being adjustably attached to the main frame. In like manner,rear wheels are capable of being mounted with respect to the main framein a plurality of positions, and front wheels are also capable of beingmounted with respect to the main frame in a plurality of positions.

The present invention also provides an apparatus for selectivelypositioning the rear wheels of a wheelchair to selectively alter thecenter of gravity thereof. This apparatus comprises a pair of spacedapart plates which are mounted on the main frame. A plurality of axlereceiving locations are provided on each of the spaced apart plates andare capable of receiving a rear wheel axle in each of such locations. Arear wheel axle is provided and is capable of extending in the rearwheel axle locations on each of said plates. Further, a quick releasemeans is associated with the rear wheel axles to enable quick releaseand replacement of rear wheels on these rear wheel axles. Thus, the rearwheel axles can be easily removed from one location and replaced inanother axle receiving location so that the response and center ofgravity and the wheel base on said frame can be easily and quicklyaltered. In more detail, the axle receiving locations comprises aplurality of pairs of spaced apart openings in each of the spaced platesto receive the rear wheel axles. These plates are located on oppositesides of the main frame. Further, a retaining member may be associatedwith each of the plates. Each retaining member is also provided with aplurality of openings which are aligned with the openings on the plateswith which the retaining members are associated.

In another embodiment of the invention, the quick release means arepreferably located on each rear wheel axle. The quick release means maycomprise at least one retaining pin extending outwardly from the axleand capable of being retracted therein to permit removal of the wheel onthe axle. A manually actuable means, such as a shiftable rod on eachshaft, causes said retaining pin to be retracted upon actuation thereof.

As indicated previously, the front wheels on each of the wheelchairs canalso be adjustably positioned. Particularly, the front wheels can beselectively positioned to alter the angle of attack of the wheelchairrelative to a ground plane. As used herein, the term "ground plane"refers to a ground surface of other supporting surface upon which thewheelchair could be used and is generally a horizontal plane. Further,the position of the front wheels can be altered relative to the rearwheels in order to change the wheel base. Thus, for example, the rearwheels can be shifted closer to or further from the front wheels and/orthe front wheels can be shifted closer to or further from the rearwheels. In addition to the above, the front wheels and the rear wheelscan be shifted simultaneously in the same direction to affect thepositions of the front and rear wheels relative to the main frame inorder to vary the riding characteristics of the wheelchair.

The apparatus for selectively positioning the front wheels comprises apair of wheel post housings on the main frame means. A post extendsoutwardly from each of these wheel post housings. A separate bracket iscarried by each of the posts and is rotatable about a generally verticleaxis relative to the associated wheel post housing. Each of the bracketshas a pair of spaced apart plates with a plurality of aligned aperturesin said spaced apart plates. A separate wheel assembly is also providedfor each bracket, and each wheel assembly is comprised of a wheel and afront wheel axle capable of being disposed in any of the plurality ofaligned apertures. In this way, it is possible to adjust the plane ofthe frame, and hence, the angle of attack of the wheelchair relative tothe ground plane.

In another embodiment of the invention, these front wheel brackets aresized so that different sized wheels can be removably mounted withrespect to the brackets. Further, the wheel posts are generallyvertically located, and said posts extend downwardly and outwardly fromthe associated wheel post housing.

The rear wheels are normally adapted for engagement with the ground orother supporting surface and are capable of being operatively engaged bya user for propelling the wheelchair. In like manner, the front wheelsare normally adapted for engagement with the ground or other supportingsurface. The front wheels typically have a diametral size which issubstantially less than the rear wheels. In one embodiment of theinvention, a foot rest member of foot support member may be provided onthe frame means and extend forwardly therefrom as aforesaid. A pair ofrollers may be provided on the foot rest member and are normally spacedabove the ground or other supporting surface when the wheelchair is usedfor normal transport. However, these rollers enable the wheelchair to betipped forwardly by the user thereof so that the rear wheels aretemporarily raised from the ground or other supporting surface, and therollers are thereupon lowered into engagement with the ground or othersupporting surface. This may be a temporary condition which may exist inathletic activities or the like. Moreover, in the event that the user ofthe wheelchair becomes overzealous and attempts to tip the wheelchair,as for example, in an athletic activity, the rollers will prevent theentire wheelchair from tipping over.

In still a further embodiment of the invention, it is also possible toprovide an outwardly extending frame on the rear portion of thewheelchair, if desired. This latter frame may also be provided withrollers on the lower portion thereof. Thus, these rollers on therearwardly extending frame would also engage the ground or othersupporting surface when the front wheels were temporarily tipped abovethe ground or other supporting surface.

The rollers which are typically used on a wheelchair, as aforesaid, havea diametral size which is substantially less than the front wheels.Further, the front wheels and rollers are mounted so that they arecapable of rotation in the same direction as the rear wheels and arealso capable of rotation about a vertical axis. The rollers in this casemay adopt the form of casters.

It is also possible to cant (often referred to as "camber") the rearwheels so that the lower portions are disposed outwardly with respect tothe main frame, and the upper portions are disposed inwardly toward theframe. This type of canting or cambering of the rear wheels alsoprovides increased stability, particularly when the wheelchair is usedin athletic activities. In addition to the canbering, the wheels can betoed in or out, as may be decreed.

This invention possesses many other advantages and has other purposeswhich may be made more clearly apparent from consideration of the formsin which it may be embodied. These forms are shown in the drawingsforming and accompanying part of the present specification. They willnow be described in detail for the purposes of illustrating the generalprinciples of the invention, but it is to be understood that suchdetailed descriptions are not to be taken in a limiting sense.

BRIEF DESCRIPTION OF THE DRAWINGS

Having this described the invention in general terms, reference will nowbe made to the accompanying drawings (four sheets) in which:

FIG. 1 is a side elevational view of a wheelchair constructed inaccordance with and embodying the present invention;

FIG. 2 is a front elevational view of the wheelchair of FIG. 1;

FIG. 3 is a fragmentary front elevational view showing the front wheelsof the wheelchair in an alternate position;

FIG. 4 is a fragmentary vertical sectional view taken along line 4--4 ofFIG. 1;

FIG. 5 is a perspective view of a rear wheel mounting bracket formingpart of the wheelchair of the present invention;

FIG. 6 is a top plan view, partially broken away and in section, andshowing the means for attaching the mounting bracket of FIG. 5 to themain frame of the wheelchair;

FIG. 7 is a side elevational view, partially broken away and in section,and showing a quick release means for removably locking a rear wheel tothe wheelchair and taken along line 7--7 of FIG. 1;

FIG. 8 is a vertical sectional view of one form of quick release means;

FIG. 9 is a side elevational view, partially broken away, and showingthe shifting of an arm assembly forming part of the wheelchair of thepresent invention;

FIG. 10 is a perspective view of a portion of a seat structure formingpart of the wheelchair of the present invention; and

FIG. 11 is a side elevational view, partially broken away and insection, and showing a portion of the seat pad forming part of the seatstructure of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now in more detail and by reference characters to the drawingswhich illustrate practical embodiments of the present invention, Adesignates a wheelchair having a main frame 10. The main frame 10 ismore fully illustrated in FIGS. 1 and 2 and comprises a pair oflongitudinally extending lower bars 12 and a pair of upwardly spacedlongitudinally extending upper bars 14. At the rearward end, the upperand lower bars 14 and 12 are connected by a pair of transversely spacedapart vertically extending bars or rigid members 16. At their forwardends, the upper and lower sets of bars 12 and 14 are connected bysomewhat upright rigid members or bars 18, in the manner as more fullyillustrated in FIGS. 1 and 2. In like manner, intermediate the rearupright rigid members or bars 16 and the front bars 18 are a pair ofintermediate upright bars 20 which connect each of the opposite sides ofthe upper and lower bars 12 and 14.

The intermediate bars 20 are spaced somewhat closer to the rear uprightbars 16. In this respect, the front bars 18 are referred to as beingupright, even though they are not truly vertically disposed, inasmuch asthey do have a vertical component and do extend between the lower andupper bars 12 and 14.

Extending between the lower bars 12 is a transversely extendingconnecting bar 22. In like manner, extending between the rear uprightbars 16 is a transversely connecting bar 24.

Each of the aforesaid bars are essentially welded with respect to oneanother in order to form the overall main frame 10, in the manner asillustrated. Thus, these main bars may be formed of various metals, suchas steel, stainless steel, aluminum, or the like. In one of the morepreferred embodiments of the invention, each of the components of themain frame is preferably formed for aluminum or titanium in order toprovide the light weight to the wheelchair, and also to provide thenecessary rigidity. In addition, the use of these metals also permitsthe wheelchairs to withstand a substantial amount of physical abuse, asfor example, the kind encountered in sports activities.

Each of the aforesaid bars is also rectangular in construction andtubular. However, if desired, the bars could be formed of a solid metal.Moreover, the rectangular shape has been found to be not onlyaesthetically desirable, but highly effective to provide the necessarydegree of ridigity.

This main frame 10 can be used in order to construct a variety ofdifferent sized wheelchairs by merely adjustably positioning the seatstructure and the foot support structure as hereinafter described inmore detail. Moreover, this same main frame may be used in theconstruction of wheelchairs which function for normal transport andwhich can also be used in athletic activities. Otherwise, the same mainframe can be used in the manufacture of a wheelchair primarily designedfor athletic activities or otherwise, a wheelchair normally andprimarily designed for normal transport.

Provided for attachment to the lower ends of the front uprights 18 is afoot support structure 26, and which foot support structure is morefully illustrated in FIGS. 1 and 2 of the drawings. The foot supportstructure 26 is comprised of a generally horizontally disposed footsupport member 28 which integrally merges through arcuately shaped bends29 into a pair of upright posts 30. By further reference to FIG. 2, itcan be observed that the posts 30 are aligned with the open lower endsof the uprights 18. Moreover, the posts 30 are capable of extending intothe tubular uprights 18 so as to adjust the overall distance between themain frame 10 and the horizontal foot support member 28. In addition,the posts are secured within the tubular uprights 18 in the desiredpositions by means of set screws or similar forms of fasteners 31. Itcan be observed, that by adjusting the position of the posts 30 withinthe lower ends of the uprights 18, that it is possible to adjust theoverall distance of the foot support member 28 to a seat (hereinafterdescribed) and also to adjust the overall effective horizontal distanceof the foot support member from the main frame.

The foot support member is also preferably formed of light weightmetals, such as aluminum, or the like. Moreover, for ease ofconstruction, simplicity, and low cost, the foot support member 26 canbe formed almost as an integral structure with the tubular member beingbent for insertion into the posts.

Mounted on foot support member 28 is a front roller assembly 32, andwhich is comprised of a bracket 33 rigidly mounted on the horizontal rod28. Carried by the bracket is a pin 34 which, turn, carries a pair ofrollers 36. By reference to FIGS. 1 and 2, it can be observed that therollers 36 are raised above the ground or other supporting surface whenthe rear wheels and the front wheels are located in contact with theground or other supporting surface. However, it can be observed thatduring any activity if the rear wheels should be temporarily elevatedfrom the ground in an attempt to tip the chair by the user, the frontrollers 36 will contact the ground to prevent the chair from tippingover. Again, means could be provided for adjusting the relative heightof the rollers 36 such that they could provide the desired amount ofclearance, and yet also prevent an inadvertent complete tipping over thewheelchair, which could result in injury to the user.

It should be understood that a similar frame could be mounted on a rearportion of the main frame 10 so as to mount rear rollers similar to thefront roller assembly 32. In this way, if the wheelchair were tippedrearwardly, such rear rollers would also prevent the wheelchair fromtipping over in the rearward direction.

The illustrated and described wheelchair A also comprises a seatstructure 38 which is more fully illustrated in FIGS. 1 2, 10 and 11.The seat structure 38 generally comprises a buttocks and leg supportingseat section 40 and a back supporting section 42. The back supportingsection 42 generally comprises a pair of tubular posts 44 which aregenerally circular in shape and are adapted to extend into the openedupper ends of the rear uprights 16. Tubular posts 44 also extend intopockets 46 formed along the opposite transverse ends of a backrest pad48. Moreover, the pockets 46 merge into shoulders 50 at their lowerends. Mounted on the posts 44 are collars 52 which are adjustablypositioned thereon by means of set screws 54. In this way, the collars52 will control the distance that the posts 44 extend into the pockets46. Moreover, the collars 42 can abut the upper ends of the uprights 16when the back support 42 shifted to its lowermost position. Thus, thecollars 52 also provide a means to adjust the overall height of the backsupport pad 48.

The back support pad 48 may also be provided with a securement strap 56which is adapted to extend around crossbar 24. Further, the securementstrap 56 would be provided with an attachment means 60 which, in thiscase, adopts the form of a Velcro releasably attachable strip.

The back support pad 48 is preferably comprised of an outer cover, suchas a cloth material, and an inner pad (not shown), and which is formedof a resilient material such as styrofoam or polyurethane foam. In thisway, the outer cover of the back seat support 48 could be changed ifdesired.

The frame also includes a horizontal frame section 62 or so-called seatsupport section comprised of a pair of horizontally disposedlongitudinally extending and transversely spaced apart rods 64 which aresecured at their rearward ends to the uprights 16 thereby forming asingle seat frame. At their forward ends, the rods 64 integrally mergeinto generally downwardly struck posts 66 which are adapted to extendinto the opened upper ends of each of the front forward uprights 18, inthe manner as best seen in FIGS. 1 and 2 of the drawings. Moreover,while not absolutely necessary, in some cases, it may be desirable tosecure the posts 66 in their telescoped position within the uprights 18by means of suitable fasteners, such as set screws, or the like.

The longitudinally extending rods 64 also telescopically merge intoforward extending frame members 68 located parallel to the abovementioned frame members 14, as more fully illustrated in FIGS. 1, 2, 10and 11. The supporting seat section 40 is provided with an outer cover70 which is provided with sewn pockets 72 in order to receive the rods68 along with the longitudinally extending rods 64. The pockets 72 aredesigned so that the rods can be removed therefrom in order to permitthe mounting of a new outer cover 70. Suitably enclosed within the cover70 is a pad 74 similar to the pad used in the back section 48. Thus,this pad can be formed of a foam type material, such as a urethane foam,or the like. The cover 70 is provided with a front opening and areleasable flap 76 in order to permit access to the pad 74. Moreover,the flap 76 is securable to the underside of the cover 70 by means of asuitable securement means, such as a Velcro attachment, or the like.

This construction is highly effective in that it enables the pad 74 tobe easily interchangeable. In many cases, the users of wheelchairs areincontinent or otherwise have difficulty controlling body discharge,such as urine. As a result, the pad 74, and for that matter, the seatcover 70 may become soiled and require replacement. This constructionenables very easy removal of one soiled pad and insertion of a new seatpad 74. In like manner, this construction also enables easy andconvenient exchange of one supporting seat structure for another.

The wheelchair can be provided with an arm rest structure 80 orso-called side rail structure or arm support structure. One embodimentof the arm rest structure which may be used in the illustrated anddescribed wheelchair is more fully illustrated in FIG. 1 of thedrawings. The arm rest or side rail structure 80 is generally comprisedof a pair of vertically disposed tubular retainer sleeves 82 which aremounted on the rear portion of the wheelchair as more fully illustratedin FIG. 1.

The supporting sleeves 82 are provided at their lower ends withforwardly struck brackets 84 for securement to the frame of thewheelchair by means of conventional fasteners, as for example, by screws86. In this way, the tubular supporting sleeves 82 may be removablymounted on the wheelchair when it is desired to use an arm supportingstructure 80.

Secured to the forward ends of each of the opposite horizontallydisposed rods 14 are plates 88 which carry at their forward ends,upwardly disposed tubular sleeves 90. In like manner, the tubularsleeves 92 also cooperate with the sleeves 90 and are located to receiverods 44, which are, in turn, removably disposed within the sleeves 82.The sleeves 92 are horizontally disposed, and the sleeves 90 and 92 inthe respective pairs, removably attach rods 94 by means of set screws 96and rivets 98, respectively. In this way, the rod 94 along withcooperating sleeves 90 and 92 and the sleeve 82 each form a side rail onopposite sides of the wheelchair A.

The arm supporting structures 80 are also shiftable out of the way inorder to permit entry into and removal of a person from a wheelchair.For this purpose, the plate 88 may be removably secured tolongitudinally extending bars 14 by removable locking pins 100. Theselocking pins 100 are conventional in their construction. Typically, theyare provided with a manually actuable member, such as a push-button, inorder to permit release of the locking pin. Thus, when the locking pin100 has been removed, the plate 88 is disengaged from the rod 14 therebypermitting the entire arm portion, including the sleeves 90 and 92 andthe rod 94, to be shifted in a lateral direction about a vertical axisextending through the sleeve 82. In like manner, the arm supportingstructures can be returned to their position on the sides of thewheelchair by merely locking the plates 88 into the bars 14 with thelocking pins 100.

On the forward ends of the wheelchair A, on each of the opposite sidesthereof, are front wheel assemblies 102 and which are more fullyillustrated in FIGS. 1-3 of the drawings. Each front wheel assembly 102generally comprises a mounting hub 104 which is rigidly secured to aninverted U-shaped bracket 106 as best seen in FIG. 4. In this case, thebracket 106 is adapted to be disposed over either of the longitudinallyextending bars 12. Moreover, the mounting hub 104 may be secured in aselected position along the longitudinal bar 12 by means of a bolt 108which extends through the bracket 106 and into the mounting hub 104.Disposed within and extending downwardly from the mounting hub 104 is arod 110 which is secured within the hub 104 by means of a nut 112 at athreaded upper end of the rod 110. The rod 110 is, in turn, secured atits lower end to a wheel supporting bracket 114 which is generally of aninverted U-shape, as also best seen in FIGS. 2-4 of the drawings. Thewheel mounting bracket 114 is provided with a first pair of lower axlereceiving apertures and an upwardly located second pair of axlereceiving apertures 116. In this case, each of the apertures in therespective pairs are located on opposite sides of the wheel mountingbracket 114. A wheel assembly 118 is comprised of a wheel axle 120 and afront wheel 122 is mounted in one of the pairs of apertures in the lowerpairs of apertures 116, as shown on each of the brackets.

The second pair of apertures 116 which are located upwardly from thelower pair are adapted to receive axles and wheels of larger diameter.In this way, the front wheels can either be mounted in the upperapertures such that a forward tilt is provided to the wheelchair,otherwise, larger wheels could be so mounted. It should be understoodthat additional pairs of apertures could be provided in each of thewheel mounting brackets 114 as may be desired in order to furtheradjustably position the wheels, or to otherwise, provide for differentdiameter wheels.

By means of the above construction, it can be observed that the frontwheels can be shifted closer to or further from the rear wheels in orderto change the overall wheel base of the wheelchair. Further, theshifting of the front wheels relative to the rear wheels may also affectthe angle of attack of the wheelchair as hereinafter described in moredetail. Thus, for example, if the rear wheels are changed in verticalposition, the position of the front wheels relative to the rear wheelswill affect the angle of attack.

By further reference to FIGS. 2 and 3 of the drawings, it can beobserved that the front wheels can be reversed so as to be locatedeither inwardly or outwardly of the main frame 10. FIG. 2 illustratesthe front wheels or so-called "casters" mounted exteriorly on theopposite longitudinal sides of the frame 10. By merely loosening thebolt 108 and removing the bracket 106, it is possible to rotate each ofthe front wheel assemblies and mount them on the interior of the lowerrails 12 as illustrated in FIG. 3 of the drawings. This latterarrangement is preferred when the wheelchair is to be used in athleticactivities in order to provide greater clearance, as for example, inbouncing a basketball moving a tennis racket, or the like. In this way,the front wheels will not interfere with any moving object or a movingarm of the user of the wheelchair.

The wheelchair A of the present invention is also provided with a pairof rear wheels 130 and which are retained on the wheelchair on the mainframe 10 by means of rear wheel mounting assemblies 132 which are morefully illustrated in FIGS. 1 and 5-7 of the drawings. In this case, therear wheels each comprise a center hub 134 which is capable of receivinga rear wheel axle 136 as hereinafter described in more detail. Thecenter hub is connected to a relatively rigid rim 138 by means of aplurality of spokes 140. Suitably mounted on the rim 138 is a tire,which is preferably a rubber tire 142. In a conventional manner, it ispreferable to have the tire 142 removably mounted for purposes ofreplacement. Also suitably mounted on each of the wheels 130 is a handengagable circumferentially extending rim 144 which is adapted to beengaged by the hands of the user for causing roation of the wheels abouttheir central axis and thereby causing propelling movement of thewheelchair.

The rear wheel mounting means 132 preferably comprises a mountingbracket 146 which is, in turn, mounted to the main frame 10 of thewheelchair. Each of the brackets 146 are mounted to the upstanding bar16 and the intermediate upstanding bar 20 in the manner as illustratedin FIG. 1 of the drawings. Each of the brackets 146 are provided with aface plate 148 and a spaced-apart mating plate 150 connected to theplate 148 by means of a pair of rearwardly extending arms 152. Moreover,the plate 148 is secured to the upstanding bars 16 and 20 by means ofsheet metal screws, bolts or similar fasteners 154. For this purpose,the plate 148 is provided with a plurality of bolt receiving apertures156 in the manner as illustrated in FIG. 5 of the drawings. Further, itcan be observed that the inwardly located mating plate 150 has a smallersize than the plate 148 so as to be snugly disposed between the twoupstanding bars 16 and 20.

Each of the plates 148 and 150 are provided with a plurality of alignedapertures 158 for receiving a rear wheel axle 136. These apertures 158and 160 define rear wheel axle receiving locations such that the rearwheel axles 136 can be located in any of the sets of apertures 158 and160.

By reference to FIG. 7 of the drawings, it can be observed that themounting bracket 146 is not mounted in a truly vertical position.Rather, the bracket 146 is canted somewhat such that the rear wheel axle136 is also located at an angular relationship with respect to a truehorizontal. In this way, the rear wheels 130 are canted somewhat in themanner as illustrated in FIG. 2 of the drawings and as hereinafterdescribed in more detail. The mounting brackets 146 may be mounted tothe main frame by using one or more shims 162 in the manner asillustrated in FIG. 7. In this way, the mounting bracket 146 isangulated away from the true vertical position, and hence, the axle 136is located so that the rear wheels are canted with the upper ends of thewheels being located inwardly and the lower ends of the wheels beingstruck outwardly. It has been found in connection with the presentinvention that it is desirable to actually cant the wheels in thisfashion in order to provide greater stability to the wheelchair,particularly when the latter is used in sports activities such as racingevents, and the like. The rear wheels may be cambered at an angle ofabout 0° to about 10° per wheel from a truly vertical position, andpreferably, from an angle of 3° to about 5° per wheel in order toachieve the most desirable results.

Along with the cambering of the rear wheels, these wheels can also betoed inwardly or outwardly by using shims (not shown) on the mountingbrackets 146. Typically, it is desirable to toe the rear wheelsoutwardly when the rear wheels are cambered. Preferably, the rear wheelsshould be towed out at a ratio of one-third of the camber. Thus, forexample, for every degree of camber, there should be a toe-out of aboutone-third degree.

The rear wheel axles 136 actually form part of a quick release lockmechanism 164 which is more fully illustrated in FIGS. 7 and 8 of thedrawings. In this case, the quick release lock mechanism includes a pin166 which is concentrically located within a bore in the axle 136 suchthat the axle 136 is effectively an outer sleeve for the release pin166. In addition, a washer or outer sleeve 168 is disposed upon the axle136 for limiting the axial movement thereof when in position to hold arear wheel thereon. Further, a locking sleeve 170 having a knurled outersurface is also threadedly disposed on the threaded left hand end 172 ofthe axle 136. Thus, by positioning the locking sleeve 170, it ispossible to provide for the proper location of the abuttment sleeve 168.At its left hand end, the axle 136 is provided with a handle 174, andwhich receives an outwardly extending end 176 of the release pin 166.This outwardly extending end 176 functions as a release button which ismanually actuable to axially displace the pin 166 to thereby release apair of detent balls 178 at the right-hand end of the axle 136. Further,the release pin 166 is provided with a plurality of grooves 182 suchthat when pushed inwardly, the grooves 182 become aligned with the balls178 permitting them to fall inwardly. However, when the release pin 166is biased to the left by means of a compression spring 184, the ballsare displaced by a shoulder 186 thereby biasing the balls 178 outwardly.In this way, the balls function as locking elements.

Thus, when it is desired to mount a rear wheel in any of the rear wheellocations, the pin 166 can be pushed inwardly in through the axle 136thereby permitting the locking elements 178 to fall radially inwardlytoward the center of the axle. This will permit the axle to be removedfrom any of the aligned apertures 158 and 160. Moreover, the axle canthen be removed from the hub 134 of the rear wheels. In like manner,when it is desired to mount the rear wheel on the wheelchair, therelease pin 166 is pushed inwardly by manually engaging the outer end176. Again, the locking elements 178 will be permitted to fall radiallyinwardly permitting the hub 134 to be mounted on the axle 136 and alsopermitting the axle to be inserted through the aligned apertures 158 and160. Thus, when the outer end 176 is released and the release pin 166 isbiased to the right, by means of the compression spring 184, the lockingelements 178 will be biased outwardly thereby retentively locking therear wheel on to the wheelchair.

It can be observed by means of the above construction, that it ispossible to selectively position the rear wheels on the wheelchairframe. By positioning the rear wheels so that they are located in thelower and rearwardmost corner of the brckets 146, the wheelchair willassume a more standard riding position in the same manner asconventional wheelchairs. Thus, the wheelchair will function for normalday to day activity. By positioning the axle in the upper andforwardmost apertures 158 and 160 of the bracket 146, the rear portionof the wheelchair will be effectively shifted upwardly thereby raisingthe center of gravity. However, this is desirable in some situations.Thus, the center of gravity of the wheelchair can be easily altered. Inaddition, by shifting the rear wheel axles either rearwardly orforwardly in any of the selected axle receiving locations, it is alsopossible to effectively change the overall wheelbase of the wheelchairin order to obtain the desired riding characteristics.

Thus, there has been illustrated and described a unique and novelwheelchair which can be constructed in several different sizes fromstandard sized component sets and on which is capable of functioning forconventional movement as well as for athletic activities, and whichtherefore fulfills all of the objects and advantages sought therefor. Itshould be understood that many changes, modifications, variations, andother uses and applications will become apparent to those skilled in theafter after considering this specification and the accompanyingdrawings. Therefore, any and all such changes, modifications,variations, and other uses and applications which do not depart from thespirit and scope of the invention are deemed to be covered by theinvention which is limited only by the following claims.

Having thus described my invention, what I desire to claim and secure byLetters Patent is:
 1. An apparatus for selectively positioning the rearwheels of a wheelchair having a frame means to selectively alter thecenter of gravity thereof, said apparatus comprising:(a) a first pair ofconnected and spaced apart plates provided for attachment to one side ofsaid frame means and a second pair of connected and spaced apart platesprovided for attachment to an opposite side of said frame means, (b) aplurality of axle receiving openings on each of said pairs of spacedapart plates and the openings in the plates of each pair being alignedso as to be capable of receiving a rear wheel axle in each of said axlereceiving, openings, (c) a separate rear wheel axle capable of extendingoutwardly from the rear wheel axle openings on each of said pairs ofplates, (d) flange means on at least one of the plates of each of saidpairs for fastener attachment to a frame means of said wheelchair suchthat the pairs of plates can be attached to the frame means in any of aplurality of selected locations to accommodate the size and intended useof a user, (e) quick release means associated with said rear wheel axleto enable quick release and replacement of rear wheels on said rearwheel axle, such that said axle can be easily removed from one locationand replaced in another axle receiving location on said plates so thatthe response and center of gravity and wheel base on said frame can beeasily and quickly altered.
 2. The apparatus of claim 1 furthercharacterized in that a matrix of at least four by four of said alignedspaced apart openings are on each of said spaced apart plates of eachpair to receive said rear wheel axles.
 3. The apparatus of claim 1further characterized in that said flange means is provided with boltholes and said pair of plates are attached to opposite sides of saidframe means by bolts.
 4. The apparatus of claim 3 further characterizedin that said flange means includes a pair of flanges provided on each ofsaid pairs and each of said flanges are provided with bolt holes forattachment to each of the opposite sides of said wheelchair by means ofbolts.
 5. The apparatus of claim 4 further characterized in that saidquick release means is located on said rear wheel axle.
 6. The apparatusof claim 5 further characterized in that said quick release meanscomprises at least one retaining pin extending outwardly from said axleand capable of being retracted therein to permit removal of a wheel onsaid axle, and manually actuable means on said axle for causing saidretaining pin to be retracted upon actuation of said manually actuablemeans.
 7. An apparatus for selectively positioning the front wheels of awheelchair having a frame means to selectively alter the angle of attackof the wheelchair relative to a ground plane, said apparatuscomprising:(a) a pair of wheel post housings on said frame means, (b) apost extending outwardly from each of said wheel post housing and beingrotatable relative to said wheel post housings, (c) a separate bracketcarried by each of said posts and being rotatable about a generallyvertical axis relative to the associated wheel post housing, and each ofsaid brackets having a pair of spaced apart plates with a plurality ofpairs of aligned apertures in said spaced apart plates, (d) a separatewheel assembly for each said bracket and each wheel assembly beingcomprised of a wheel and an axle capable of being disposed in any of theplurality of pairs of aligned apertures to thereby adjust the plane ofthe frame and hence the angle of attack of the wheelchair relative to aground plane, and (e) a mounting member extending from each of the wheelposts housings and being adapted for attachment to said frame means in afirst position and a second position, the wheel post housings beinglocated outwardly of the sides of the frame means when the associatedmounting members are in the first position and being located inwardly ofthe sides of the frame means when the associated mounting members are inthe second position, the positions of said front wheels in either thefirst or second position being a function of steering radius andsteering stability.
 8. The apparatus of claim 7 further characterized inthat said brackets are sized so that different sized wheels can beremovably mounted with respect to each of said brackets.
 9. Theapparatus of claim 7 further characterized in that said wheel posthousings are generally vertically located, and said posts extenddownwardly and outwardly from the associated wheel post housing.
 10. Theapparatus of claim 9 further characterized in that said pair of alignedapertures are vertically located in said spaced apart plates.
 11. Theapparatus of claim 8 further characterized in that said apparatus isadapted to selectively position rear wheels on the frame means of awheelchair, said apparatus further comprising:(1) a pair of spaced apartplates on said frame means, (2) a plurality of axle receiving locationson each of said spaced apart plates and which are capable of receiving arear wheel axle in each of said axle receiving locations, (3) a rearwheel axle capable of extending between the rear wheel axle location oneach of said plates for carrying a rear wheel, and (4) quick releasemeans on said rear wheel axle to enable quick release and replacement ofrear wheels on said rear wheel axle.
 12. The apparatus of claim 7further characterized in that said mounting means comprises a somewhatinverted U-shaped member capable of fitting over a bar of the framemeans and being attached thereto by means of a fastner.
 13. A wheelchaircapable of being used for sports activities and also for normaltransport, said wheelchair comprising:(a) a frame means, (b) a seatmounted on said frame means for supporting an individual using suchwheelchair, (c) a foot rest member of said frame means and extendingforwardly therefrom, (d) a pair of rear wheels mounted on said framemeans capable of being engaged by a user for propelling said wheelchair,(e) a pair of front wheels mounted on said frame means for normallybeing in engagement with the ground or other supporting surface andhaving a diametral size substantially less than said rear wheels, saidrear wheels and front wheels normally being in engagement with theground or other supporting surface when said wheelchair is propelledforwardly or in turns in normal transport, and (f) a pair of rollers onsaid foot rest member and normally being spaced above the ground orother supporting surface a relatively slight distance above the lowerends of said front wheels when said wheelchair is used for normaltransport, said wheelchair capable of being tipped by the user thereofso that said rear wheels are temporarily raised a relatively slightdistance from the ground or other supporting surface and said rollersare lowered into temporary engagement with the ground or othersupporting surface.
 14. The wheelchair of claim 13 further characterizedin that said seat is located in a normal sitting location for supportingthe user when said rear wheels and front wheels are in contact with theground or other supporting surface.
 15. The wheelchair of claim 13further characterized in that said rollers have a diametral sizesubstantially less than said front wheels.
 16. The wheelchair of claim15 further characterized in that said rear wheels are mounted so thatthey are adapted for rotation in the same direction such that they arenot capable of rotation about a vertical axis, but that such rollers andfront wheels are capable of being rotated about a vertical axis.
 17. Thewheelchair of claim 15 further characterized in that hand rims aremounted on said rear wheels for engagement by a user to propel thewheelchair.
 18. A wheelchair capable of being used for sport activitiesand, also for normal transport, said wheelchair comprising:(a) a framemeans, (b) a seat mounted on said frame means for supporting anindividual using such wheelchair, (c) a foot rest member on said framemeans and extending forwardly therefrom, (d) a first pair of spacedapart and connected plates on one side of said frame means and a secondpair of spaced apart and connected plates on the opposite side of saidframe means, (e) a plurality of axle receiving openings on each of saidspaced apart plates and the openings in the plates of each pair beingaligned so as to be capable of receiving a rear wheel axle in each ofsaid axle receiving openings, (f) a rear wheel axle capable of extendingbetween the rear wheel axle openings on each of said pairs of plates,(g) flange means on at least one of the plates of each of said pairs andbeing attached by fasteners to said frame means, (h) quick release meansassociated with said rear wheel axles to enable quick release andreplacement of rear wheels on said rear wheel axles, such that the axlescan be easily removed from one pair of openings and replaced in anotheraxle receiving pair of openings on said plates so that the response andcenter of gravity and wheel base of said frame can be easily and quicklyaltered, (i) a rear wheel provided for disposition on each of said rearaxles for normally being in engagement with the ground or othersupporting surface and capable of being operatively engaged by a userfor propelling said wheelchair, (j) a pair of wheel post housings onsaid frame means, (k) a post extending outwardly from each of said wheelpost housings, (l) a separate bracket carried by each of said posts andbeing rotatable about a generally vertical axis relative to theassociated wheel post housings, each of said brackets having a pair ofspaced apart plates with a plurality of pairs of aligned apertures insaid spaced apart plates, (m) a separate front wheel assembly for eachsaid bracket and each wheel assembly being comprised of a front wheeland front wheel axle capable of being disposed in any of the pluralityof pairs of aligned apertures to thereby adjust the plane of the frame,and hence, the angel of attack of the wheelchair relative to a groundplane, said front wheels being normally in engagement with the ground orother supporting surface and having a diametral size substantially lessthan said rear wheels, said rear wheels and front wheels normally beingin engagement with the ground or other supporting surface when saidwheelchair is propelled forwardly or turns in normal transport, and (n)a pair of rollers on said foot rest member and normally being spacedabove the ground or other supporting surface a relatively slightdistance above the lower ends of said front wheels when said wheelchairis used for normal transport, said wheelchair capable of being tipped bythe user thereof so that said rear wheels are temporatily raised arelatively slight distance from the ground or other supporting surfaceand said rollers are lowered into engagement with the ground or othersupporting surface.
 19. The wheelchair of claim 18 further characterizedin that said seat is located in a normal sitting location for supportingthe user when said rear wheels and front wheels are in contact with theground or other supporting surface.
 20. The wheelchair of claim 18further characterized in that said rollers have a diametral sizesubstantially less than said front wheels.
 21. The wheelchair of claim18 further characterized in that said rear wheels are mounted so thatthey are adapted for rotation in the same direction such that they arenot capable of rotation about a vertical axis, but that such rollers andfront wheels are capable of being rotated about a vertical axis.
 22. Thewheelchair of claim 18 further characterized in that a matrix of atleast four by four of said aligned spaced apart openings are on each ofsaid spaced apart plates of each pair to receive said rear wheel axles.23. The wheelchair of claim 18 further characterized in that said quickrelease means is located on said rear wheel axles and each comprising atleast one retaining pin extending outwardly from said axle and capableof being retracted therein to permit removal of a wheel on said axle,and manually actuable means on each said shaft for causing saidretaining pin to be retracted upon actuation of said manually actuablemeans.
 24. The wheelchair of claim 18 further characterized in that saidbrackets are sized so that different sized front wheels can be removablymounted with respect to each of said brackets.
 25. A wheelchaircomprising:(a) a main frame being comprised of:(1) a plurality oflongitudinally extending rigid members, (2) a plurality of transverselyextending rigid members rigidly secured to said longitudinally extendingmembers, (3) a plurality of first generally upright members on a rearportion of said frame, (4) a plurality of second generally uprightmembers on a front portion of said frame, (b) a seat structure capableof being attached to and adjustably positioned on said frame, said seatstructure being comprised of:(1) a seat frame having a plurality offirst posts, each capable of being telescopically fitted with respect toa separate one of said first generally upright members and adjustablylocated with respect thereto, a plurality of second posts with eachbeing telescopically fitted with respect to a second one of said secondgenerally upright members and adjustably located with respect thereto,(2) a seat pad carried by said seat frame, (3) arm support means on eachof the opposite sides of the wheelchair for attachment to said first andsecond generally upright members, and (c) a foot support structurecapable of being attached to and adjustably positioned at the frontportion of said frame, said foot support structure comprised of:(1) aplurality of second posts, each capable of being fitted with respect toa separate one of said second generally upright members and adjustablylocated thereon, (2) a foot receiving member connected to said secondposts whereby several different sized wheelchairs can be constructedwith commonly sized main frames and commonly sized foot supportstructures and commonly sized seat structures.
 26. The wheelchair ofclaim 25 further characterized in that said seat frame has additionalparts capable of being fitted with respect to upper ends of said firstupright tubular members.
 27. The wheelchair of claim 26 furthercharcterized in that said upright members are tubular and said posts arecapable of being fitted into said upright members.
 28. The wheelchair ofclaim 25 further characterized in that arm rests are capable of beingadjustably attached to said main frame.
 29. The wheelchair of claim 25further characterized in that rear wheels are capable of being mountedwith respect to said main frame in a plurality of positions.
 30. Thewheelchair of claim 29 further characterized in that front wheels arecapable of being mounted with respect to said main frame in a pluralityof positions.
 31. A wheelchair capable of being used for athleticactivities and also for normal transport, said wheelchair comprising:(a)a frame means, (b) a seat mounted on said frame means for supporting anindividual using such wheelchair, (c) a first pair of connected andspaced apart rear axle mounting plates on one side of said frame meansand a second pair of connected and spaced apart rear axle mountingplates on an opposite side of said frame means, (d) flange means on atleast one of the plates of each pair for securement to said frame means,(e) a plurality of axle receiving openings on each of said spaced apartrear axle mounting plates, the openings in the plates of each pair beingaligned so as to be capable of receiving a rear wheel axle in said axlereceiving openings on opposite sides of said wheelchair, at leastcertain of said rear axle openings being located in a generallyhorizontal plane so as to primarily alter the wheel base of thewheelchair when a rear wheel axes is shifted between the rear axlereceiving openings, (f) a pair of rear wheel axles capable of beinglocated in said rear wheel axle openings, (g) a rear wheel provided fordisposition on each said rear wheel axles for normally being inengagement with the ground or other supporting surface, (h) a pair offront wheel mounting means, (i) a plurality of front wheel axlereceiving positions with respect to each said front wheel mounting meansto enable front wheel axles to be mounted at any of said front wheelaxle receiving positions, (j) front wheel axles capable of being locatedin said front wheel axle receiving a position, (k) a front wheel capableof being located with respect to each said front wheel axle, (l) aseparate front wheel post housing on each of the opposite sides of thewheelchair frame means, (m) a front wheel post extending outwardly ofeach of said post housings and being rotatable relative to saidhousings, said posts being secured to said front wheel post housings atthe respective sides of the wheelchair, and (n) a pair of mountingmembers forming part of said front wheel mounting means and eachextending from one of the wheel post housings and being adapted forattachment to said frame means in a first position and a secondposition, the wheel post housings being located outwardly of the sidesof the frame means when the associated mounting members are in the firstposition and being located inwardly of the sides of the frame means whenthe associated mounting members are in the second position, thepositions of said front wheels in either the first or second positionbeing a function of steering radius and steering stability.
 32. Thewheelchair of claim 31 further characterized in that quick release meansis associated with said rear wheel axles to enable quick release andreplacement of rear wheels on said rear wheel axles, such that the rearwheel axles can be easily removed from one set of openings and replacedin another set of axle receiving openings so that the response andcenter of gravity and wheel base on said frame can be easily and quicklyaltered.
 33. The wheelchair of claim 32 further characterized in thatsaid rear wheels and front wheels are normally in engagement with theground or other supporting surface when said wheelchair is propelledforwardly or in turns in normal transport, and a foot rest member is onsaid frame means and extends forwardly therefrom, a pair of rollers areprovided on said foot rest member and are normally spaced above theground or other support surface a relatively slight distance above thelower ends of said front wheels when said wheelchair is used for normaltransport, said wheelchair capable of being tipped by the user thereofso that said rear wheels are temporarily raised a relatively slightdistance from the ground or other supporting surface and said rollersare temporarily lowered into engagement with the ground or othersupporting surface.
 34. A wheelchair capable of being used for sportsactivities and also for normal transport, said wheelchair comprising:(a)a frame means, (b) a seat mounted on said frame means for supporting anindividual using such wheelchair, (c) a first pair of connected andspaced apart plates attached to said frame means in a canted position sothat wheels operatively mounted thereon would be canted, (d) a secondpair of connected and spaced apart plates attached to said frame meansin a canted position so that wheels operatively carried thereby would becanted, (e) a plurality of axle receiving openings on each of said pairsof spaced apart plates and capable of receiving a rear wheel axle ineach of said axle receiving openings, (f) a rear wheel axle capable ofextending outwardly from the rear wheel axle openings on each of saidpairs of plates, (g) quick release means associated with said rear wheelaxles to enable quick release and replacement of rear wheels on saidrear wheel axle, such that said axles can be easily removed from onepair of openings and replaced in another axle receiving pair of openingson said plates so that the response and center of gravity and wheel baseon said frame can be easily and quickly altered, (h) flange means on atleast one of the plates of each of said pairs for attachment to saidframe means of said wheelchair, (i) a rear wheels mounted on each saidrear wheel axles and capable of being operatively engaged by a user forpropelling said wheelchair, said rear wheel axles and the wheels mountedthereon being canted so that the lower portions of the wheels redisposed outwardly with respect to the frame means and the upperportions are disposed near said frame, and (j) a pair of front wheelsmounted on said frame means for normally being in engagement with theground or other supporting surface and having a diametral sizesubstantially less than said rear wheels, said front wheels capable ofbeing mounted in a first position outwardly of said frame means and asecond position inwardly of said frame means, the positions of saidfront wheels in either the first or second position being a function ofsteering radius and steering stability.
 35. The wheelchair of claim 35further characterized in that said rear wheel axles are mounted on saidplates such that they are inclined downwardly and inwardly toward saidframe means.
 36. The wheelchair of claim 35 further characterized inthat(a) a foot rest member is on said frame means and extends forwardlytherefrom, and (b) a pair of rollers are on said foot rest member andnormally are relatively slightly spaced above the ground or othersupporting surface when said wheelchair is used for normal transport andcapable of engaging the ground or other supporting surface when saidwheelchair is tipped forwardly and where the rear wheels are thenrelatively slightly raised above the ground or other supporting surface.37. A method of constructing a wheelchair having a main frame and a seatstructure and a foot support structure, said method comprising:(a)inserting rear posts of a seat structure into the upper ends of aplurality of first generally upright members on a rear portion of saidframe, (b) inserting front posts of said seat structure into upper endsof second generally upright members on a front portion of said frame andwhere said front posts are operatively connected to said rear posts, (c)positioning said rear and front posts so that a seat on said seatstructure is at a desired location and securing said rear posts, (d)inserting posts of a foot support structure into the lower ends of saidsecond generally upright members on a front portion of said frame, (e)positioning said posts of said foot support structure so that a footsupport member thereof is at a desired location and securing said lastnamed posts whereby several different sized wheelchairs can beconstructed with commonly sized main frames and foot support structuresand seat structures, (f) inserting rear wheel axles in a desired one ofa plurality of rear axle receiving locations on each of the oppositesides of the frame, (g) mounting a rear wheel on each of the rear wheelaxles, and (h) mounting front wheels on each of the opposite sides ofthe frame at a desired one of a plurality of positions on the framebetween the front and rear portions thereof.
 38. The method of claim 37further characterized in that said method comprises insertion of a seatpad forming part of said seat structure into a seat cover therefor andreleasably sealing an opening on said seat cover.
 39. The method ofclaim 38 further characterized in that said generally upright membersand the posts capable of being fitted therein are adjustablytelescopically arranged.
 40. The method of claim 38 furthercharacterized in that said method comprises adjustably attaching armrests to main frame.
 41. The method of claim 38 further characterized inthat said method comprises mounting rear wheels with respect to saidmain frame in one of a plurality of vertically spaced apart positionsand one of a plurality of horizontally spaced apart positions.
 42. Themethod of claim 41 further characterized in that said method comprisesmounting front wheels with respect to said main frame in one of aplurality of positions between front and rear portions of the frame andeither inwardly or outwardly of said frame.
 43. A mechanism forremovably mounting the rear wheels of a wheelchair to a frame means ofthe wheelchair, said mechanism comprising:(a) a pair of spaced apart andconnected plates provided for securement to said frame means, each ofsaid plates being provided with a plurality of spaced apart axlereceiving openings in said plate and which are capable of receiving arear wheel axle in each of said axle receiving openings, (b) a rearwheel axle capable of being inserted into and through any of saidopenings and extending outwardly from said plates, (c) a pin extendingoutwardly from said axle retentively holding said rear wheel axle in aselected opening and thereby holding a wheel on said axle, (d) manuallyactuable quick release means associated with said rear wheel axle toenable shiftable movement of said pin and thereby enable quick removaland replacement of a rear wheel on said rear wheel axle, and to alsopermit said axle to be easily removed from an opening and replaced inthe same or another opening on said plate, and (e) a pair of flangeswith each on an opposite side of one of the plates and having means toenable attachment to a frame means of the wheelchair.
 44. The apparatusof claim 43 further characterized in that two pairs of said plates areprovided with each having axle receiving openings to receive said rearwheel axles such that each one of the pairs is to be located on oppositesides of the frame means.
 45. The apparatus of claim 44 furthercharacterized in that a pair of rear wheel axles are provided so that anindividual axle extends between the rear wheel openings on each of theopposite sides of said wheelchair.
 46. The apparatus of claim 43 furthercharacterized in that said quick release means is connected to said pinto cause retraction of said pin when actuated.
 47. A wheelchaircomprising:(a) a main frame, (b) a first pair of connected and spacedapart plates attached to one side of said frame and a second pair ofconnected and spaced apart plates attached to an opposite side of saidframe, (c) a plurality of axle receiving openings on each of said spacedapart plates and openings in each of the plates of a pair being alignedto be capable of receiving a rear wheel axle in each of said axlereceiving openings, (d) a rear wheel axle extending outwardly from therear wheel axle openings on each of said pairs of plates, (e) flangemeans on at least one of the plates of each of said pairs for fastnerattachment to a frame means of said wheelchair, (f) quick release meanson said rear wheel axle to enable quick release and replacement of rearwheels on said rear wheel axle, such that said axles can be easilyremoved from one location and replaced in another axle receivinglocation on said plates so that the response and center of gravity andwheel base on said frame can be easily and quickly altered, said quickrelease means comprising:(1) at least one retaining pin extendingoutwardly from said axle and capable of being retracted therein topermit removal of a wheel on said axle, (2) manually actuable means onsaid axle for causing said retaining pin to be retracted upon actuationof said manually actuable means, (g) a pair of wheel post housings onsaid frame means, (h) a post extending vertically downwardly from eachof said wheel post housings and being rotatable with respect to theassociated post housing, (i) a separate bracket carried by each of saidposts and being rotatable about a generally vertical axis relative tothe associated wheel post housing, and each of said brackets having apair of spaced apart plates with a plurality of pairs of verticallyspaced apart aligned apertures in said spaced apart plates, (j) aseparate wheel assembly for each said bracket and each wheel assemblybeing comprised of a wheel and an axle capable of being disposed in anyof the plurality of pairs of aligned apertures to thereby adjust theplane of the frame and hence the angle of attack of the wheelchairrelative to a ground plane, (k) a mounting member extending from each ofthe wheel post housings and being adapted for attachment to said framemeans in a first position and a second position, the wheel post housingsbeing located outwardly of the sides of the frame means when theassociated mounting members are in the first position and being locatedinwardly of the sides of the frame means when the associated mountingmembers are in the second position, the first or second positions beinga function of steering radius and steering stability, said rear wheelsand front wheels normally being in engagement with the ground or othersupporting surface when said wheelchair is propelled forwardly or inturns in normal transport, (l) a seat mounted on said frame forsupporting an individual using such wheelchair, (m) a foot rest memberof said frame and extending forwardly therefrom, and (n) a pair ofrollers on said foot rest member and normally being spaced above theground or other supporting surface a relatively sight distance above thelower ends of said front wheels when said wheelchair is used for normaltransport, said wheelchair capable of being tipped by the user thereofso that said rear wheels are temporarily raised a relatively slightdistance from the ground or other supporting surface and said rollersare lowered into engagement with the ground or other supporting surface..Iadd.
 48. An apparatus for selectively positioning the main drivingwheels of a wheelchair having a frame to selectively alter the center ofgravity thereof, said apparatus comprising:(a) a bracket having meanshaving a plurality of spaced apart axle holes extending therethrough andprovided for attachment to one side of said frame and which holes aresized so as to be capable of receiving a rear wheel axle, (b) a secondbracket having means having a plurality of axle receiving holesextending therethrough and provided for attachment to an opposite sideof said frame and which holes are sized so as to be capable of receivinga wheel axle, (c) a separate wheel axle capable of extending outwardlyfrom any one of the wheel axle holes in each of said brackets, (d) meansfor attachment of said brackets to a frame means of said wheelchair, and(e) a separate quick release means associated with each of said wheelaxles to enable quick release and replacement of the driving wheels onsaid wheel axles, each of said quick release means comprising a manuallyactuatable element which operates to permit release of the axle from thehole when actuated and which permits re-insertion into the same oranother hole by pushing the axle into said same or another hole where itbecomes locked therein, such that each of said axles can be easilyremoved from a hole in a bracket and replaced in another axle receivinghole in said bracket so that the response and center of gravity andwheel base on said frame can be easily and quickly altered. .Iaddend..Iadd.
 49. The apparatus of claim 48 further characterized in that oneof said holes is horizontally spaced from another of said holes witheach sized to receive said wheel axles. .Iaddend. .Iadd.50. Theapparatus of claim 48 further characterized in that another one of saidholes is vertically spaced from said first named hole and sized toreceive a wheel axle. .Iaddend. .Iadd.51. The apparatus of claim 48further characterized in that said manually actuatable elements arepushable pins which operates to permit release and permit removal ofsaid axles when pushed. .Iaddend. .Iadd.52. The apparatus of claim 51further characterized in that each of said quick release means comprisesat least one retaining element extending outwardly from said axle andcapable of being retracted therein to permit removal of a wheel on saidaxle, and said manually actuatable element of each said quick releasemeans causes said retaining element to be retracted upon actuation ofsaid manually actuatable element. .Iaddend. .Iadd.53. The apparatus ofclaim 48 further characterized in that said releasable axles are rearwheel axles and said quick release means are located on said rear wheelaxles. .Iaddend. .Iadd.54. A wheelchair in which the center of gravitythereof, can be selectively altered, said wheelchair comprising:(a) amain frame, (b) a separate bracket attached to each of the oppositesides of said frame, each of said brackets having a plurality of axlereceiving openings which are sized to receive a driving wheel axle, (c)a driving axle capable of extending outwardly from any one of the axlereceiving openings in each of said brackets, (d) a separate drivingwheel carried by each said driving wheel axle, and (e) a quick releasemeans associated with said driving wheel axles to enable quick releaseand replacement of said driving wheels on said driving wheel axles, suchthat each of said axles can be easily removed from one opening andreplaced in another axle receiving opening in a bracket so that theresponse and center of gravity and wheel base on said frame can beeasily and quickly altered, said quick release means comprising amanually actuatable element which operates to permit release of the axlefrom the opening when actuated and which permits re-insertion into thesame or another opening by pushing the axle into said same or anotheropening where it becomes locked therein, whereby manual pushing of saidmanually actuatable element and pulling on the driving wheel axle issufficient to cause release and ultimate removal of an axle and pushingof the axle into another opening enables re-insertion and locking of theaxle in that opening. .Iaddend. .Iadd.55. The wheelchair of claim 54further characterized in that means is provided on each of the bracketsfor attachment to a frame of said wheelchair such that the brackets canbe attached to the frame in a desired location. .Iaddend. .Iadd.56. Thewheelchair of claim 55 further characterized in that each of saidbrackets can be attached to the frame of the wheelchair so as to achievea desired camber of the driving wheels. .Iaddend. .Iadd.57. Thewheelchair of claim 55 further characterized in that said means forattachment is a flange means which is provided with bolt holes and saidbrackets are attached to said frame by bolts. .Iaddend. .Iadd.58. Thewheelchair of claim 54 further characterized in that a matrix of atleast four by four of said aligned spaced apart openings are on each ofsaid brackets to receive said axles. .Iaddend. .Iadd.59. The wheelchairof claim 54 further characterized in that said manually actuatableelement comprises a pushable pin extending axially through each of saidaxles, and locking means extending outwardly of said axle to hold sameat an opening in a bracket and actuatable by said pin when pushed tocause said locking means to be retracted, such that only manual pushingof said pin and pulling on said axle is sufficient to enable release andultimate removal or re-insertion of an axle. .Iaddend. .Iadd.60. Thewheelchair of claim 59 further characterized in that said locking meanscomprises at least one retaining sphere extending outwardly from anaperture in said axle and capable of being retracted therein to permitremoval of the axle from an opening and removal of a wheel on said axlewhen said manually actuatable pin is pushed inwardly. .Iaddend..Iadd.61. The wheelchair of claim 54 further characterized in that meansis provided to adjust the position of the axle and the amount ofextension of the axle through the bracket. .Iaddend. .Iadd.62. Thewheelchair of claim 61 further characterized in that the means to adjustcomprises a threaded sleeve for threaded adjustment. .Iaddend. .Iadd.63.The wheelchair of claim 54 further characterized in that said releasableaxles are rear wheel axles and said quick release means are located onsaid rear wheel axles. .Iaddend. .Iadd.
 4. An apparatus for selectivelypositioning the main driving wheels of a wheelchair having a frame toselectively alter the center of gravity thereof, said apparatuscomprising:(a) a bracket having opening means thereon and extendingtherethrough and provided for attachment to one side of said frame andwhich opening means is sized to be capable of receiving a rear wheelaxle in any of a plurality of selected locations, (b) a second brackethaving opening means therein and extending therethrough and provided forattachment to an opposite side of said frame and which opening means isalso sized so as to be capable of receiving a wheel axle in any of aplurality of selected locations, (c) a separate wheel axle capable ofextending outwardly from each one of said opening means in each of saidbrackets, (d) means for attachment of said brackets to a frame of saidwheelchair, and (e) a separate quick release means associated with eachof said wheel axles to enable quick release and replacement of thedriving wheels on said wheel axles, each of said quick release meanscomprising a manually actuatable element which operates to permitrelease of the axle from the opening means when actuated and whichpermits re-insertion into the opening means in the same location oranother location by pushing the axle into said opening means where itbecomes locked therein, such that each of said axles can be easilyremoved from the opening means in a bracket and replaced in the openingmeans in the same or another location in said bracket so that theresponse and center of gravity and wheel base on said frame can beeasily and quickly altered. .Iaddend. .Iadd.65. The apparatus of claim64 further characterized in that the opening means permits movement ofan axle longitudinally with respect to the frame of a wheelchair..Iaddend. .Iadd.66. The apparatus of claim 64 further characterized inthat the opening means permits movement of an axle both vertically andlongitudinally with respect to the frame of a wheelchair.